#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-12;

int main() {
	int v[2][6] = {{1,2,3,4,5,6},{4,4,5,5,6,6}};
	
	int n, k;
	cin >> n >> k;
	
	srand((unsigned int)time(NULL));
	
	int win = 0, cnt = 0;
	
	REP(i, 1000000) {
		int sum1 = 0;
		REP(j, n - k) sum1 += v[0][rand() % 6];
		REP(j, k) sum1 += v[1][rand() % 6];
		
		int sum2 = 0;
		REP(j, n) sum2 += v[0][rand() % 6];
		
		if (sum1 > sum2) win++;
		cnt++;
	}
	
	printf("%.15f\n", (double)win / cnt);
	
	return 0;
}